The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ...The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.展开更多
The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual...The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non-geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering （KRISO）’s container ship （KCS） was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.展开更多
Fishing boats have unique features that make them prone to changing loading conditions.When the boat leaves the port,the empty fish tank gradually fills up during fishing operations which may result in parametric roll...Fishing boats have unique features that make them prone to changing loading conditions.When the boat leaves the port,the empty fish tank gradually fills up during fishing operations which may result in parametric roll(PR).This dangerous phenomenon that can lead to capsizing.The present study aims to understand better the behaviour of parametric roll in fishing boats and its relation to changing loading conditions.The study considers the effects of displacement and the GM/KM ratio on parametric roll,as well as the longitudinal flare distribution at the waterline.Two assessments to detect the parametric roll occurrence in early stage were carried out by using the level 1 assessment of parametric roll based on the Second Generation of Intact Stability criteria(SGIS)from International maritime Organisation(IMO)and the Susceptibility criteria of Parametric roll from the American Bureau of Shipping(ABS).Then,the CFD method is used to predict the amplitude of the parametric roll phenomenon.The results provide important insights to fishing vessel operators on how to manage loading conditions to maintain stability and avoid hazardous situations.By following the guidelines outlined in this study,fishing boats can operate more safely and efficiently,reducing the risk of accidents and improving the overall sustainability of the fishing industry.展开更多
The incompressible unsteady Reynolds-averaged Navier-Stokes(URANS)simulations are performed for a free-running container ship in maneuvering conditions:the starboard and portside turning circle simulations with 35...The incompressible unsteady Reynolds-averaged Navier-Stokes(URANS)simulations are performed for a free-running container ship in maneuvering conditions:the starboard and portside turning circle simulations with 35°rudder deflection.The validation variables include trajectory,motions,and propeller performances,and the prediction shows acceptable agreements against the experimental data.During the steady-state part of the turning,the inertial forces balancing the local forces are reported to quantitatively assess the centrifugal force which appears from the force equilibrium between the rudder,propeller,and the bare-hull.The study on the local flow focuses on finding the correlations between the propeller inflow and the propeller performance to investigate the differences in propeller performances during the portside and starboard turning.The preliminary simulations,performed with the grid triplet,comprise propeller open-water,resistance,and self-propulsion simulations,from which the validation studies and the studies for the local force and the local flow are fulfilled and applied for the main simulations.Both propeller and rudder are fully discretized and controlled,mimicking the experiment.Level-set,overset approach and Mentor’s SST model are employed for the free-surface capturing,large motion prediction,and turbulence closure.展开更多
Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotation...Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotational speed and the presence of wave.When targeting the same mean Froude number in the wave condition,the propeller requires the increased propeller rotational speed for the operation at the low advance ratio due to the added resistance.The test is performed at five different wavelengths in head waves and four different headings in the oblique waves.For the validation study,the time series of the validation variables is decomposed with discrete Fourier transform to extract the harmonic values.Validation variables are global parameters,including motions,propeller thrust,and torque coefficients,added power variables,and self-propulsion factors which show reasonable agreement against the experiment results and produces a similar error from the self-propulsion simulation.The local force study shows that the added resistance mostly appears at the bow due to the bow plunging during the short head wave and resonance condition.The contributions of the gravitational force and the buoyant force are found to increase as the stern motion exceeds the bow motion during the long head wave condition.The oscillation of the propeller performances shows correlation with the first harmonic amplitude of the propeller inflow.Heave,pitch,and roll decay tests are performed prior to the main test to assess the natural frequencies of the ship.Same as Part 1,a discretized propeller is used.展开更多
基金supported by the China Scholarship Council(Grant No.202306320084).
文摘The turning performance of a ship is an important aspect of its maneuverability,and accurately predicting the hydrodynamic forces during ship turning motion is of great significance for the safe maneuvering design of ships.This paper investigated the hydrodynamic performance of a KRISO container ship in steady turning using experimental and numerical approaches.The rotating arm tests were carried out in rotating arm basin of Zhejiang University,while the numerical simulations were conducted in commercial computational fluid dynamics software.Hydrodynamic forces and moments,hull surface wave height,wave patterns,and vorticity are studied under different velocities,radii,and drift angles.The results show that the increase in velocity has a significant impact on the forces and moments of the hull.The changes in longitudinal and transverse forces reflect the complex fluid dynamic interactions between the hull and water.Under conditions of small radius and large drift angle,the hull experiences greater forces and moments,indicating that stability and maneuverability will be more challenged during sudden turns.This study can provide experimental data and numerical simulation references for the research of ship turning maneuvers.
基金the National Natural Science Foundation of China，the Fundamental Research Funds for the Central Universities，the Specialized Research Fund for the Doctoral Program of Higher Education
文摘The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non-geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering （KRISO）’s container ship （KCS） was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.
文摘Fishing boats have unique features that make them prone to changing loading conditions.When the boat leaves the port,the empty fish tank gradually fills up during fishing operations which may result in parametric roll(PR).This dangerous phenomenon that can lead to capsizing.The present study aims to understand better the behaviour of parametric roll in fishing boats and its relation to changing loading conditions.The study considers the effects of displacement and the GM/KM ratio on parametric roll,as well as the longitudinal flare distribution at the waterline.Two assessments to detect the parametric roll occurrence in early stage were carried out by using the level 1 assessment of parametric roll based on the Second Generation of Intact Stability criteria(SGIS)from International maritime Organisation(IMO)and the Susceptibility criteria of Parametric roll from the American Bureau of Shipping(ABS).Then,the CFD method is used to predict the amplitude of the parametric roll phenomenon.The results provide important insights to fishing vessel operators on how to manage loading conditions to maintain stability and avoid hazardous situations.By following the guidelines outlined in this study,fishing boats can operate more safely and efficiently,reducing the risk of accidents and improving the overall sustainability of the fishing industry.
基金This work was supported by the Office of Naval Research(Grant Nos.N00014-17-1-2083,N00014-17-1-2084).
文摘The incompressible unsteady Reynolds-averaged Navier-Stokes(URANS)simulations are performed for a free-running container ship in maneuvering conditions:the starboard and portside turning circle simulations with 35°rudder deflection.The validation variables include trajectory,motions,and propeller performances,and the prediction shows acceptable agreements against the experimental data.During the steady-state part of the turning,the inertial forces balancing the local forces are reported to quantitatively assess the centrifugal force which appears from the force equilibrium between the rudder,propeller,and the bare-hull.The study on the local flow focuses on finding the correlations between the propeller inflow and the propeller performance to investigate the differences in propeller performances during the portside and starboard turning.The preliminary simulations,performed with the grid triplet,comprise propeller open-water,resistance,and self-propulsion simulations,from which the validation studies and the studies for the local force and the local flow are fulfilled and applied for the main simulations.Both propeller and rudder are fully discretized and controlled,mimicking the experiment.Level-set,overset approach and Mentor’s SST model are employed for the free-surface capturing,large motion prediction,and turbulence closure.
基金This work was supported by the Office of Naval Research(Grant Nos.N00014-17-1-2083,N00014-17-1-2084).
文摘Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotational speed and the presence of wave.When targeting the same mean Froude number in the wave condition,the propeller requires the increased propeller rotational speed for the operation at the low advance ratio due to the added resistance.The test is performed at five different wavelengths in head waves and four different headings in the oblique waves.For the validation study,the time series of the validation variables is decomposed with discrete Fourier transform to extract the harmonic values.Validation variables are global parameters,including motions,propeller thrust,and torque coefficients,added power variables,and self-propulsion factors which show reasonable agreement against the experiment results and produces a similar error from the self-propulsion simulation.The local force study shows that the added resistance mostly appears at the bow due to the bow plunging during the short head wave and resonance condition.The contributions of the gravitational force and the buoyant force are found to increase as the stern motion exceeds the bow motion during the long head wave condition.The oscillation of the propeller performances shows correlation with the first harmonic amplitude of the propeller inflow.Heave,pitch,and roll decay tests are performed prior to the main test to assess the natural frequencies of the ship.Same as Part 1,a discretized propeller is used.
